Better barns: Not every boiler is created equal
By Ben Kaiser
By Ben Kaiser
It seems like every second conversation about installing new equipment in barns eventually leads to boilers. Now I’ll grant, it may be because I have a tender spot in my heart for boilers due to my plumbing and gasfitting background. They have become so much more technical over the past few years.
Not every boiler is created equal, and not every boiler makes sense in every application. Here’s why, using water as an example. It takes one BTU/hr to raise one pound (lb) of water one degree Fahrenheit (F), once water hits 212°F it then requires 970 BTUs for water to change into steam at 212°F. This also works in reverse, when you go from steam at 212°F to water at 212°F, there is 970 BTUs of heat energy that gets released.
This is the principle that makes high efficient boilers highly efficient. A condensing boiler takes the products of combustion, the smoke, and condenses them. In very simple terms, it turns the gas into a liquid, and then uses the energy released and puts that into your system instead of out into the air.
I know, I know… You’re asking why does this even matter – how does this affect me? Doesn’t this mean that a high efficiency boiler really is the best for any and all applications? Well, to answer that we need a tiny bit more information. Namely, at what temperature do the products of combustion in a natural gas appliance turn to water? A rule of thumb number that I use is 135°F. Lower than this and we get nice condensation. Higher than this and the vapour stays in vapour form all the way through my system and makes its way outside.
So, we know that it’s by taking the energy from the phase change that we can add more energy into the system –in the boiler we are changing from vapour to liquid. We also know that with natural gas that number is around the 135°F mark. Now, let’s take this into real world applications.
For a typical in-floor or under-slab heating system the water runs at, let’s say, 120°F on those cold wintery nights. That high efficiency boiler is humming along in cruise control, dumping gallons of condensate water down the drain. Because the water in the concrete floor is low, we can use the energy from the condensate gases turning into a vapour and dump that energy into the water.
In cases where we have an outdoor reset, where the boiler automatically lowers the temperature as it gets warmer outside, the boiler gets even more efficient. The lower the water temperature the easier it is to dump the heat into the water. Now as long as the system water temperature is below 135°F we can cause the boiler to condense and make it more efficient. But what happens if you’re using high temperature fan coils or radiation pipe? Simply put, nothing. There is no condensation happening because the dew point hasn’t been reached – the temperature is too high.
In practical terms, it means this: If your system is designed to use high temperatures, a high efficient boiler doesn’t save you much. A note of caution, though – a conventional boiler is not supposed to start condensing. The condensate water can be quite acidic, in the neighbourhood of four on the pH scale. Condensation boilers are designed to handle this. Conventional boilers would eventually have their heat exchangers eaten out.
In my opinion, when it comes to a house I like the IBC boilers due to the ease with which the electrician can wire them. When talking about a line of boilers, I look to the Lochinvar boilers.
They offer everything from small wall hung residential boilers to big multi-million BTU boilers. If you’re asking about cast-iron sectional boilers, my favorite is the Viessmann line. If you want something that is simple and easy to fix, in my mind nothing beats the Super Hot line.
Ultimately, boiler selection comes down to two factors. Number one: What application is this boiler designed for? Is it high temperature, low temperature or high flow? Number two: What do you or your plumber feel comfortable servicing and repairing?
Ben Kaiser is a master gasfitter and master plumber. He works with his father Martin and his three brothers at Kaiser Ag and specializes in poultry barn construction and installations.